Abstract: A hydraulic power pack having a framework, a prime mover driving a hydraulic pump, a hydraulic circuit including a reservoir and flow and return connectors. The power pack also includes an oil cooling system comprising a thermostatically operated valve and an oil cooler in the hydraulic circuit. The valve diverts flow of fluid to the oil cooler when the temperature of the fluid rises above a predetermined limit, before returning the fluid to the reservoir. The oil cooler has a pair of heat exchangers mounted at the respective outlets of a double acting centrifugal fan directly coupled to and driven by the prime mover.

Abstract: A hydraulic power pack having a prime mover driving a plurality of hydraulic pumps, a hydraulic circuit including a reservoir connected to an inlet of said pumps, an outlet circuit from said pumps, one or more pressure relief valves in the outlet circuit and a plurality of external connectors on the outlet circuit. The connectors and the relief valves are arranged so that different hydraulic flow and pressure characteristics may be obtained from each connector. Each connector has a flow and a return line, the latter being connected to the reservoir. Valves provided in the hydraulic circuit are responsive to zero flow in the return line of each connector and are adapted to divert the hydraulic flow directly to the reservoir without restriction.

Abstract: A hydraulic power pack having a prime mover, at least one hydraulic pump, a reservoir and associated valving and hydraulic circuitry, in which each of the components is mounted on one of two parts of a frame. The two parts of the frame are hinged together at one side, thereby enabling the frame to be opened to allow access to the components for maintenance.

Abstract: The control valve mechanism of, for example a hydraulic motor for a chain saw, includes a two-position spool having a hollow interior permanently connected to reservoir and a cylindrical wall formed with ports which are closed in one valve position and open in the other valve position. During movement of the spool into the motor-operating position, a lubricant passageway is opened before the motor is fully operational.